1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to searching rights objects stored in a portable storage device using object location data.
2. Description of Related Arts
Recently, digital rights management (DRM) has been actively researched and developed, and used in commercial services. DRM needs to be used in commercial services because of the following various characteristics of digital content. Unlike analog data, the digital content can be copied without loss and can be easily reused, processed and distributed. However, a large amount of cost, labor, and time are needed to produce the digital content. When the digital content is copied and distributed without permission, a producer of the digital content may lose profit, and the producer's enthusiasm may be discouraged. As a result, development of digital content business may be hampered.
There have been several efforts to protect digital content. Conventionally, digital content protection has been concentrated on preventing non-permitted access to digital content, and permitting only people who have paid charges to access the digital content. However, when a person who has paid charges intentionally distributes the digital content to other people, these other people can use the digital content without paying charges. To solve this problem, DRM was introduced. In DRM, any one is allowed to freely access encrypted digital content, but a license referred to as a rights object is needed to decrypt and execute the digital content. Accordingly, the digital content can be more effectively protected by using DRM, as compared to the conventional method.
A portable storage device is a connectable/disconnectable device such as a portable phone, a computer, or a digital camera which can store data of various types of digital equipment and is portable. The portable storage device includes a storage space for storing data and a portion performing an operation and control. A multimedia card (MMC) is a portable storage device which stores multimedia data to be used for various types of digital equipment, overcoming limitations of conventional hard disks or compact disks. The MMC also includes an operation part that is not included in conventional storage media, thereby having the ability to perform control. Recently, a security function was added to the MMC, thereby developing a secure MMC that secures digital content during storage and transmission and protects copyright. With the development of the secure MMC, rights management on digital content becomes possible in a storage device and digital equipment. Hereinafter, digital equipment such as a digital camera, a portable phone, a computer and a digital camcorder will be collectively referred to as a “host device.”
Recently, memory cards including a flash memory have popularized as portable storage devices. Different from a dynamic random access memory (DRAM) or a synchronization random access memory (SRAM), these portable storage devices can maintain data without power supply. However, they are disadvantageous in that input and output speeds of data are slower than in the DRAM.
A rights object stored in a portable storage device is information to be referenced whenever content is reproduced, which requires repetitive reading, writing or modifying operations. To effectively perform these repetitive operations, it is necessary to reduce time consumed in searching for a specific rights object.
A conventional method of providing a cache function through an SRAM to thereby increase input/output speeds of a memory card has been presented in Korean Patent publication No. 2002-0020104. In the conventional method, the SRAM is initialized when the memory card is connected to a digital device and thereafter functions as a cache memory storing specific data therein during read and write operations, thereby increasing input/output speed.
The conventional method may increase the input/output speed when searching again data which has been previously searched but it cannot decrease inherent delay caused in data searching.
In particular, since the portable storage device storing rights objects therein under the DRM system repeatedly performs input/output operations for a specific rights object and operations for searching each rights object with various conditions, there is a need for a method to improve the speeds of inputting/outputting objects and searching the objects.